The passenger compartment of motor vehicles provides a space which provides protection to the occupants from environmental elements. To this end, the body of the vehicle defining the passenger compartment is preferably tight fitted at the door (by the term “door” is meant an expansive definition which includes doors, hatches, liftglass, decklids (trunklid), liftgates, etc.) and window seams, and provides an enclosure which keeps out dust, wind and water, and minimizes the passenger perception of road noise. In this respect, the more air-tight the body, the better. However, the air-tight quality of the body defining a passenger compartment must not be too air-tight for purposes of ease of closing a door and for purposes of efficient operation of the heating, ventilation and air conditioning (HVAC) system.
When a door is closed, the movement of the door is accompanied by a substantial movement of air into the body. This in rush of air creates a pressure increase (air compression) within the body which needs release to the atmosphere, otherwise the increase in pressure will make full closure of the door difficult and also give any occupant the sensation of an ear pop at closure. Indeed, when one considers a door in the form of a decklid, the closure of the decklid can also cause air compression within the body, as for example by air flowing through the back seat.
The passengers need ventilation, and when the HVAC system is active, the fan and/or the vehicle movement draws air into the body, thereby causing an increase in air pressure within the passenger compartment. Accordingly, this incoming air needs some means of escape in order that air in the passenger compartment is able to periodically turn over, and so that the pressure does not increase to an extent that an untoward burden is placed on the function of the HVAC system.
In the prior art, the solution of choice for providing an air-tight passenger compartment which is selectively vented has been to install passive flap vents at the body wall defining the passenger compartment. FIGS. 1A and 1B depict an example of a conventional passive body ventilation flap valve 10. The flap valve 10 includes a flap housing 12 which is attached to an opening in the body 14. A pair of flaps 16 are connected at one end thereof, respectively, to the flap housing 12, preferably composed of a plastic. Each of the flaps 16 is composed of a resiliently flexible material, as for example a rubber or plastic, which is resiliently biased into the closed position (see FIG. 1A) so as to cover respective ports 18 (see FIG. 1B). When air pressure within the body (i.e., the passenger compartment) increases above atmospheric pressure, the flaps resiliently bend into an open position, as for example depicted at FIG. 1B so that air can pass out of the body through the ports 18 until the pressure becomes generally equalized. FIGS. 2A through 2D depict other examples of prior art flap valves 10a-10d, each composed of a flap housing 12a-12d with a plurality of resiliently flexible flaps 16a-16d each covering a respective port (not visible in the views).
While flap valves are simple and generally inexpensive components, they suffer from certain drawbacks. One significant draw back is that a flap valve is inherently unable to provide a high level of road noise isolation with respect to the passenger compartment. For another, the passive nature of flap valves does not allow for dynamic response to the operational status of the HVAC system. Still further, since the resiliency and response rate of the flaps of the flap valves is preset, there is always going to be some air compression inside the passenger compartment when a door is shut which will require additional door push energy to overcome; and if a door is slammed, passenger ear discomfort may be sensed. Further yet, when a door is opened, since the flap valves are essentially one-way, a suction can be created which makes the door harder to open during the initial phase of opening.
Accordingly, what remains needed in the art is a body ventilation system which is actively responsive to vehicle status parameters, including for example the door open/closed status and the HVAC system status.